dma-api: Teach the "DMA-from-stack" check about vmapped stacks

If we're using CONFIG_VMAP_STACK=y and we manage to point an sg entry
at the stack, then either the sg page will be in highmem or sg_virt()
will return the direct-map alias.  In neither case will the existing
check_for_stack() implementation realize that it's a stack page.

Fix it by explicitly checking for stack pages.

This has no effect by itself.  It's broken out for ease of review.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/448460622731312298bf19dcbacb1606e75de7a9.1470907718.git.luto@kernel.org
[ Minor edits. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index fcfa193..06f02f6 100644 (file)
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -22,6 +22,7 @@
 #include <linux/stacktrace.h>
 #include <linux/dma-debug.h>
 #include <linux/spinlock.h>
+#include <linux/vmalloc.h>
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
 #include <linux/export.h>
@@ -1164,11 +1165,32 @@ static void check_unmap(struct dma_debug_entry *ref)
        put_hash_bucket(bucket, &flags);
 }
 
-static void check_for_stack(struct device *dev, void *addr)
+static void check_for_stack(struct device *dev,
+                           struct page *page, size_t offset)
 {
-       if (object_is_on_stack(addr))
-               err_printk(dev, NULL, "DMA-API: device driver maps memory from "
-                               "stack [addr=%p]\n", addr);
+       void *addr;
+       struct vm_struct *stack_vm_area = task_stack_vm_area(current);
+
+       if (!stack_vm_area) {
+               /* Stack is direct-mapped. */
+               if (PageHighMem(page))
+                       return;
+               addr = page_address(page) + offset;
+               if (object_is_on_stack(addr))
+                       err_printk(dev, NULL, "DMA-API: device driver maps memory from stack [addr=%p]\n", addr);
+       } else {
+               /* Stack is vmalloced. */
+               int i;
+
+               for (i = 0; i < stack_vm_area->nr_pages; i++) {
+                       if (page != stack_vm_area->pages[i])
+                               continue;
+
+                       addr = (u8 *)current->stack + i * PAGE_SIZE + offset;
+                       err_printk(dev, NULL, "DMA-API: device driver maps memory from stack [probable addr=%p]\n", addr);
+                       break;
+               }
+       }
 }
 
 static inline bool overlap(void *addr, unsigned long len, void *start, void *end)
@@ -1291,10 +1313,11 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
        if (map_single)
                entry->type = dma_debug_single;
 
+       check_for_stack(dev, page, offset);
+
        if (!PageHighMem(page)) {
                void *addr = page_address(page) + offset;
 
-               check_for_stack(dev, addr);
                check_for_illegal_area(dev, addr, size);
        }
 
@@ -1386,8 +1409,9 @@ void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,
                entry->sg_call_ents   = nents;
                entry->sg_mapped_ents = mapped_ents;
 
+               check_for_stack(dev, sg_page(s), s->offset);
+
                if (!PageHighMem(sg_page(s))) {
-                       check_for_stack(dev, sg_virt(s));
                        check_for_illegal_area(dev, sg_virt(s), sg_dma_len(s));
                }